Helical end mills and face mills are well known in the industry. Conventional helical end mills include those shown on pages 182-216 in Kennametal's Milling Catalog No. 5040, copyright 1995.
One form of helical mill that has been in use for years is a helical mill where the cutting edge of each insert is axially spaced apart from the cutting edge of the next adjacent insert and where the inserts in each helix are staggered such that two or more rows are necessary to produce one complete or "all effective" cutting edge. Such a design is shown by the Kennametal 0.degree. Lead--Helical End Mills, as shown on page 188 of the above referenced Milling Catalog. One of the disadvantages of such design is that the lead insert in at least one helix must either be of a different length or offset inward and thus incapable of face milling. This is a result of the need to stagger the inserts in each helix. As a result, all of the inserts are generally not the same and thus not interchangeable, thus requiring the manufacture and inventory of multiple inserts.
These staggered helix and other conventional mills are sufficient for their intended purposes and thus many cutting processes; however, it is desirable to eliminate the need for differing inserts on a given mill.
One such solution is described in U.S. Pat. No. 5,083,887. In this solution, the cutting inserts are disposed in a helical array in which the cutting edge of each insert, with respect to the cutting tool, is spaced in the circumferential direction from the seat of the next adjacent insert and is in overlapping relationship in the axial direction with the cutting edge of the next adjacent insert, and the radially extending edges of each insert are in overlapping relation with the radially extending edges of the adjacent inserts, such that the cutting edge of all of the inserts in any one flute define a continuous, non-interrupted, cutting line of stepped configuration. This solution has become known as single flute "all-effective" milling.
Although this single flute "all effective" mill provides a helical end mill using only one type of insert and needing only one flute for "all effective" cutting, the industry continues to strive for improved "all effective" milling whether it be single flute or double flute "all effective". In particular the industry continues to strive for even better surface finishing, smoother cutting action, reduced vibrations, reduced hammering, reduced chattering, more economical cutters, more durable cutters, longer lasting cutters, and more simplistic designs for easier and faster manufacture and insert replacement.